LibrePilot Forum
Users => Vehicles - Helicopters => Topic started by: nestor81 on May 24, 2020, 09:24:31 pm
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Good, I present my new project of the heli 450 CopterX V2 with CC3D ATOM, I have flown heli in a traditional way, but I have not gone from stationary without crashing, in simulator many many hours with different translations and movements.
Previously I tried it with a Revo, but it gave me a lot of problems and I gave up, now I have a problem and I do not know if it is a question of configuration, or mechanical adjustment, I expose everything I have used and more or less like:
For assembly and configuration I have followed all the steps of:
https://frickelnundmehr.wordpress.com/startseite/trex-clone-und-cc3d/, including the position of the CC3D on the side of the heli, to avoid the greatest possible variations.
Everything is mechanically adjusted and the transmitter configured and calibrated, heli configuration, cyclic 120, inputs, outputs, flight modes, location and leveling, blade pitch +/- 11,0,11. Everything responds correctly, just like in flight data.
In the stabilization configuration, I do not know where to start, the truth is that I am in a big mess, everything is by default, except for something that I think I more or less understand, I attach an uav file so that you can see it better, but some advance little thing.
- in stabilization / basic / Responsiveness:
Attitude modified to 85
- in stabilization / Expert / Sensor Tuning:
Gyro Noise Filtering to 0.010 (As recommended as a start)
I have read almost all the posts about it, but I am not clear, they advise to start with someone's uav file, but I would have to configure all the settings again, and I do not get used to it :'(.
Is there a way to see the parameters of the uav without having to save them in the cc3d?
It has some vibrations altogether, I don't know if it will affect the problem that I expose below.
Well, the problem is the following, as I said before, everything works well, but being with the engine stopped, when I operate the engine, both in atti mode and in rate, in manual mode, the cyclic leans to one side and back, The more motor the more accused.
In flight data, it can be seen as if the heli was moving, but it is totally stopped on a table.
As a detail, the motor test was carried out with all the blades and propellers removed.
To see someone can lend me a hand.
Thank you.
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Everything responds correctly, just like in flight data.
Be aware that the PFD display there roll should look backwards. When you move the heli by hand to roll the heli left, the world rolls right.
- in stabilization / basic / Responsiveness:
Attitude modified to 85
This is the maximum bank angle in Attitude mode. For first testing, I would use much less than 85 degrees. Maybe 30 to 45 degrees.
I have read almost all the posts about it, but I am not clear, they advise to start with someone's uav file, but I would have to configure all the settings again, and I do not get used to it :'(.
Yes. There are people here that fly helis instead of quads. They have experience. I am guessing that one will come along and help within a few days. He might be able to give you advice that allows you to start from your current settings.
Is there a way to see the parameters of the uav without having to save them in the cc3d?
I am not really understanding this...
I think you are wanting to see what is in his uav file without loading it in the CC3D...
The UAV file is a human readable text file, but it is confusing to a novice. It would be better for you to save your current settings to your own UAV file so you can put it back later, then load the new UAV into the CC3D and look at your interesting pages, make some "screen capture" / "print screen" of important pages... Then put your own UAV file back into the CC3D.
It has some vibrations altogether, I don't know if it will affect the problem that I expose below.
Vibration is bad. First of all it makes it wear out more quickly. Maybe worse is that vibration past a certain amount will make the sensors go crazy and it will at least tilt, and maybe even flip over. With head and tail rotor blades removed you should be able to run any speed and Flight Data images should not move if heli does not move. Hopefully, putting blades back on does not make it vibrate worse.
Well, the problem is the following, as I said before, everything works well, but being with the engine stopped, when I operate the engine, both in atti mode and in rate, in manual mode, the cyclic leans to one side and back, The more motor the more accused.
It absolutely should not tilt for any CC3D reason (not even for vibration) just from adding motor power when in Manual mode. Long shot question: Are you using a FlySky I6 radio?
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First of all, thank you very much for the quick response.
As I wrote earlier, on the flight data screen everything moves correctly,
as you well describe.
I set the altitude at 85 to get greater range of motion for possible
emergency fixes but i will set it to 45 for startup as you advise me.
I had not really thought about that system, I will use it to see the uav data and
modify them, especially for PID data, thanks.
Regarding the vibrations, I will review all the moving physical components,
sprockets and axles especially, it is possible that it is one of the transmission components
to the tail rotor.
Sorry, I correct myself, only the tilt occurs in the atti and rate modes, in manual mode
no oscillation occurs.
The transmitter is Taranis x9d plus, with an external Flysky module, previously had Turnigy 9x, and to take advantage of the receivers ...
Again thank you very much for the quick response.
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Welcome here Nestor81!
Seems you come a long way already and are close to get it airborn :)
This Heli, does it still have the flybar or you took it off?
Seems you are using Librepilot version 15.09, no problem but can be upgraded later on to at least 16.09.
( https://librepilot.atlassian.net/wiki/spaces/LPDOC/pages/4128780/Downloads )
I had a quick look at your configuration file, thanks for sharing, it looks okay.
Please do the following adjustments.
For the Stab settings press the red parts to get it back.
(https://forum.librepilot.org/index.php?action=dlattach;topic=4890.0;attach=8596;image)
For the flight modes settings, change to axislock for all 3 modes.
replace the the Rattitude for Rate mode.
(https://forum.librepilot.org/index.php?action=dlattach;topic=4890.0;attach=8598)
Then you try to lift off in manual mode and report back what is happening
- okay?
p.s.
once you got it nicely configured, then you put the Revo board back in and do some more advanced stuff :)
d.s.
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Hello Karla,
- The project is with a heli flybarless
- LP version is 16.09, attached screenshot
Just to confirm before anything:
- In Stab settings you advise me to take the parameters marked to default parameters, is it?
- As for Enable pirouette compensation, it is selected by default,
do I have to leave it disabled? What is your function?
As soon as you confirm, more than anything to learn about LP, I make the modifications, flight test and comment.
a greeting
Thank you.
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I just made the modifications in the parameters, but I have not performed a flight test, attached video of the test on a table and the flight data screen in LP
https://youtu.be/2U3J_utTrRI
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Sorry for the delay.
Thanks for your answers. Got it.
Yes, in the Stabilisation settings, put all values in default except the 'Enable piruette comp' that should be unchecked.
In the video its show you fly in mode 3: please confirm again that that is set to
Manual, Manual, AxisLock (and Manual on thrust).
Also I think you need to confirm that you did not change the Attitude Estimation Algorithm from Basic.
You find that setting under Configuration - Attitude - Settings.
The way the horizon is starting to get unsettled while you are speeding up the head rotor looks like you have some other settings.
Once this is confirmed you should try to put it on the ground in a free space area and spin up the rotor carefully, being prepared to abort at any time of misbehaviour.
For the first try the goal is just to see if the tail is stable. When that is out of the way we move on...
Let us know what happens
Good luck
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Hi Karla, do not worry about the delay, although I am looking forward to the answers, I understand that I have to be patient.
I confirm that in the stabilization configuration, there are all the default values, I attach images to be able to see it quickly, although in the end I will also attach the uav file.
As for flight mode 3, I also confirm that Manual / Manual / AxisLock / Manual is configured.
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I have done a test to see the reaction of the tail, as you told me, although I have done it on a rotating base to prevent any accident, attached video link.
https://youtu.be/AKe-wLbTaAo
I don't know if this will help determine if there is a problem, if not please let me know and I will take the test again.
Thank you
a greeting
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Thanks for sharing the video, it helps.
Do you hold the yaw stick still or do you move it around all the time?
Seems the tail do not hold its position more than some moments...
Also the head speed of main rotor seem a bit slow, I think, or maybe you did not throttle up to to where it would like to hover/lift?
To confirm the mechanical throw of the tail servo is in the middle when almost hover, you can try do set the Yaw back to Manual and try again. Then if you need to put the yaw stick to the left or right to hold it straight you should adjust the length of the tail rod. Don't need to be totally perfect.
When that's done. Put Yaw stabilisation back to Axislock and try again and see if it holds straight when coming close to hover and you don't move the yaw stick.
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Hello, to eliminate doubts, I have carried out a new test and recorded on video.
In the video you can see that the tail does not remain stable, and the transmitter sticks are shown, which are not moved.
The gas stick is more or less in the center, at the hover point.
Previously, the tail servo was adjusted mechanically and manual mode, and was almost nailed down.
https://www.youtube.com/watch?v=0ADSWezWRwU
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That looks like a PID oscillation, although it doesn't seem to be a simple regular back and forth.
If I might give some general PID tuning suggestions.
As you have already done, do one channel at a time with the untuned channels set to manual (or for quads and actually flying where you must have some stabilization you should just use low PID values defaults, reduce them (e.g. cut P in half, cut I in half, cut D in half) till they don't oscillate). Typically you can use the same PID on both roll and pitch, but even symmetric quads are slightly asymmetric because the battery shape has more rotational inertial in one direction (moving the long way) than the other.
For helis, you should set up for a single, fixed head speed, since e.g. doubling the head speed doubles the control sensitivity and requires reduced PIDs. Always use this head speed when tuning and flying. If you must, you can tune at highest head speed and then any lower speed will not oscillate, but it will be somewhat mushier that it could be (maybe not a problem for non-stunt flight).
For helis, tune yaw first.
A caveat: High head speed and too high PID (oscillation) can be bad with some helis? During initial ground tuning of cyclic, I am guessing that you want to control throttle only, with collective neutral, so you can slam the throttle down quickly to stop an oscillation without causing hard downthrust. To test fly while tuning cyclic with tuned yaw, maybe even have the collective set to a fixed "hover" value.
For helis with flybar weights, set the weights all the way "in" or remove them completely (basically quickest control). CC3D settings can slow the controls back down if desired, but this allows CC3D to get it out of a bad situation (e.g. using an auto-leveling mode) as quickly as possible.
On the one channel you are tuning, set I and D to zero and adjust P starting from some low value and going higher and higher till it oscillates. To get there quickly, double P each time if you are comfortable with what you know about your heli's cyclic oscillations when tuning roll/pitch in particular. Find where it just starts to oscillate constantly. Cut that P number in half and save it, then increase the I term till it oscillates and back it off a little from that till it doesn't oscillate. Test quick stick blips for ringing or oscillation. Leave D set to zero. Maybe add some D if it "rings" (a small oscillation on quick stick motion that quickly decreases to zero).
For both quads and helis, if it won't hold pitch in fast forward flight, it needs more I term, at least in pitch (and probably matched in roll).
More precisely, you can use the above or many other "PID tuning" instructions on the internet. ZN tuning actually uses the oscillation period (1 / frequency) as part of the equations that give you the P, I, and D values.
Ziegler Nichols method
https://en.wikipedia.org/wiki/PID_controller#Ziegler%E2%80%93Nichols_method
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Thank you for clarification and the video - now its pretty easy to get the tail tuned.
For the yaw, just follow what TheOtherCliff is suggesting in the part beginning with
'On the one channel you are tuning...'
The head speed feels okay to start with for now.
You might need to adjust it a bit when you take the Heli out of your very nice test bench.
When you got the tail locked in, I would take it out on the floor and carefully try hover it and observe how it behaves with roll, pitch and throttle. First I would adjust throttle and collective curves so it wants to hover around mid stick. Then I would go in with the Roll axis in the same way you did the yaw.
Its easy :)
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Good guys
Sorry I didn't send any information, but I have been reviewing the ziegler-Nichols method, to learn and understand how PIDs worked, but for now it is somewhat complex for me.
I have tried to apply the second method of ZN, by oscillation, which I think is the one that fits the case of the heli system, but after lots of tests, I don't get anything, I don't know what I'm doing wrong.
I've also tried the indications of TheOtherCliff, but I also can't stabilize the yaw.
I think the problem I have is that the correct oscillations will not be recognized, since they are very varied (I know that ZN says they have to be constant, but I have had constant oscillations with the difference in speed (different critical periods) or at least it is what it seems to me.
Attached video in which I apply 3 different P values so that you can see the oscillations that occur and you can orient me a little. There are times when I intentionally wink to see the stabilizer reaction.
The P values used are:
- up to 35 second, P = 0.00390
- from 35 second to 48 second, P = 0.00703
- from the second 48, P = 0.00843
https://www.youtube.com/watch?v=FlrqQOX0avI
Greetings
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It looks like the main rotor is out of balance. At about 0:08 you can see the tail going up and down quickly (and main shaft side to side) at a particular RPM where it is the worst. I would fix that first. (Edit: Fix if it is not caused by simple blade holder alignment that straightens out at first spool up)
Then to me (no LP heli experience, you want KarlA or a few others for more heli experience), even the lowest setting that you used looked like it oscillated. I would start from there and reduce P till it goes away, and right there pop the yaw stick to make sure it feels like it has enough control after being dialed down.
The default settings are for quadcopters, which react faster (from what I understand) and can thus use higher PIDs. That is why helicopters need to dial down the default PIDs.
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I think the tail behaves just as can be expected with the different P values.
Agree with Cliff, just keep going lowering P, try half it to P = 0.002 or even more
From the point it doesn't oscillate, bring it up to the point it does, and then cut it down.
For now, I would not worry much about main rotor out of balance at some point while it spools up (maybe later).
question: on that workbench you have, can you tell when it wants to lift off or is it totally strapped down?
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hi thanks for the quick reply
The oscillations to which you refer, can be produced by the same test bench, the mechanics of the heli has been reviewed several times.
Previously, without the controller, you have not had these oscillations, I will still check everything again and do more tests with your indications
Thanks a lot
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I think the tail behaves just as can be expected with the different P values.
Agree with Cliff, just keep going lowering P, try half it to P = 0.002 or even more
From the point it doesn't oscillate, bring it up to the point it does, and then cut it down.
For now, I would not worry much about main rotor out of balance at some point while it spools up (maybe later).
question: on that workbench you have, can you tell when it wants to lift off or is it totally strapped down?
Hi Karla, as I said to Cliff, thanks for the quick response
Your contributions are helping me a lot, for the moment I am learning a lot about something new for me, I just need to put it into practice ;D
As for the test bench, the heli is fully attached to it, but the throttle level is more or less at the hover point
As soon as I get a more or less correct P value, I will remove the heli from the test bench and continue the adjustments with real flight, if it seems correct to you.
Thanks a lot
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Here again...
I have a big doubt, I started from P = 0.002 and it has oscillations, but after a few seconds it stabilizes, my question is, I have to go up until the oscillations are constant and maintained as the ZN method says, or search just where oscillations start even after it stabilizes?
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Thats progress!
Well, the way I do it (just my personal preference) is search the point where the oscillations start.
The reason is that usually if you keep it there oscillations gets worse and worse and then it can be impossible to land a Heli safely without a tail damage or worse.
But I think what you experience now is different, first it oscillates a bit and then stabilises nicely.
That is something else. It usually does that while the rotor is spooling up. Do it several times so you are sure that's the case. Then you start increase the P like 50% and see what happens.
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Hello,
I have finally decided to download my heil from my wonderful test bench !!
I have made two videos, with different parameters of P
This first video, with values of P = 300/325/350
https://www.youtube.com/watch?v=HDk_dumuJlM
And this second video, with values of P = 350/375/400
https://www.youtube.com/watch?v=zzH8f-zVIZU
I do not know if the time in flight of each of them will be enough for you to see the reactions that the heli has, but the instability produced and the lack of exponential configured to facilitate its handling, make the movements of the heli quite aggressive, and for my level, it becomes difficult to handle it.
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I would put it back on your yaw test table and get the yaw figured out first. You can clearly see the tail oscillating. The tail should lock solid and be responsive and do what is expected before moving on.
Do you know that your head speed is correct? Too slow head speed makes it mushy although to me the roll and pitch looked acceptable but not perfect at 400.
For someone who can fly without stabilization, I recommend adjusting in this order (at flying head speed) because Rate needs Manual throws to be correct, Axislock adds complexity to a correctly tuned Rate, Atti needs Rate tuned first:
- Manual, Manual, Rate adjusting Yaw only PID on rotating stand (or skittering on smooth ground)
- Manual, Manual, Rate in free hovering flight
- Then Rate, Rate, Rate
- Then Atti, Atti, AxisLock
Is there something that you know of that would make your yaw servo slower? Do you have enough amps available (in your BEC) to drive the servo at full speed against resistance? It looks like you are driving your yaw servo at 50Hz. Is is capable of using a faster signal? Is the servo mount and linkage good and tight (little slop or springiness)?
You could be using say 30 degrees for Attitude mode max bank angle, but you are using the default of 55 (you were using 85). If it is still too sensitive for you, reduce these.
Did you use a cloud config (config built into the setup program) or did you start from default settings? I think you started with defaults (as I hope) because I see that the inner loop PID is set to default in both uav files. I worry a bit because sometimes the canned settings have unexpected changes in them. I would start from default (or KarlA) settings. There are several things in settings that can make the tail oscillate, but I don't see any of them.
Does heli yaw still oscillate if you use Rate on Yaw instead of AxisLock?
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Thanks again for the videos, much easier to see what's going on, yes they are long enough.
I think it was a good time to put the Heli on the floor and try it out, and also wise to mount the four 'learning legs'.
You seem to handle it well and have enough room to test it.
I also think the roll and pitch is pretty okay as is and it seems to spool up and spool down without any imbalances, so vibrations should not be a problem, that is very good news.
But two thing comes to mind.
When I see it hover the head speed seems too low, try to increase it a bit (you can rise the throttle curve and meanwhile lower the collective curve around the hover point).
The tail oscillations should not be there. Check if there are any bindings or resistance when moving the tail rotor pitch. Unhook the tail rotor pitch rod on the servo side and try move it back and forth - it should be as smooth as cutting butter with a hot knife - really! After you have checked that and have increased head speed I think you can try your lower P values again for starters.
I would keep trying on the floor to understand how these changes will effect the behaviour. The reason I would not put it back to the bench is only because I don't have any experience to see what is going on and what needs to be changed on a bench. I think you are doing okay and can handle it, you seem very careful.
I would also keep the current stabilisation modes for now.